The present invention relates to a target to be used for forming a film comprising SiO2 as the main component by a sputtering method, a process for its production, and a film-forming method for a film comprising SiO2 as the main component by means of such a target.
Heretofore, as a material for a low refractive index film (refractive index n less than 1.6), SiO2 (n=1.46), MgF2 (n=1.38) or the like, has been known. Such a film material can be formed into a film by a vacuum deposition method or a wet-coating method, but a sputtering method is employed in many cases when a film is formed on a substrate of a large area, such as glass for buildings, glass for automobiles, a cathode ray tube (CRT) or a flat display. Among sputtering methods, a direct current (DC) sputtering method utilizing direct current discharge, is particularly suitable for film forming over a large area. Heretofore, it has been difficult to form a SiO2 film having high mechanical durability by a sputtering method in an atmosphere containing oxygen (a so-called reactive sputtering method) employing a Si target, because abnormal discharge (arcing) takes place. In recent years, a technique to suppress arcing has been developed, such as an improvement of the film-forming apparatus, whereby forming of a SiO2 film by a reactive sputtering method has been practically carried out, but the film-forming speed is not yet adequate. Further, a polycrystal Si target or a single crystal Si target to be used has had a problem that it is susceptible to cracking along grain boundaries or crystal faces. In order to make it hardly susceptible to cracking, a Si target having Al incorporated, has been proposed (JP-A-5-501587) but as Al is incorporated as an impurity into the SiO2 film, there has been a problem that the refractive index of the film increases. Further, there has been another problem that the film-forming speed is slow.
Further, it has been proposed to use a sintered SiC target to form a SiXOYCZ film (JP-A-63-113507), but, when the sintered SiC target is employed, the film-forming speed has not been adequate.
It is an object of the present invention to provide a target whereby a film comprising SiO2 as the main component and having a low refractive index, can be formed at a high speed by a sputtering method, a process for its production, and a film forming method for a film comprising SiO2 as the main component by means of such a target.
Another object of the present invention is to provide a target whereby a film comprising SiO2 as the main component and having a low refractive index, can be formed at a high speed by a sputtering method, and the durability against cracking during film forming is improved, a process for its production, and a film-forming method for a film comprising SiO2 as the main component by means of such a target.
The present invention provides a sputtering target which comprises SiC and metallic Si and which has an atomic ratio of C to Si of from 0.5 to 0.95 and a density of from 2.75xc3x97103 kg/m3 to 3.1xc3x97103 kg/m3.